The present invention relates to an apparatus for dispensing fluid through a nozzle, such as an ocular treatment apparatus for applying medicament or other substances to an eye.
There are various known devices for applying medicament to the eye. A typical eye-drop container has a flexible vial and a nozzle for releasing drops of medicament into the eye by squeezing the vial. If the user squeezes too hard, too much medicament can be released and, as a result, drip down the user's cheek. There is typically no means provided for accurately controlling the volume of each dose of medicament released into the eye and the smallest drop obtained as a result of the combined effect of gravity and surface tension is always bigger than the space available on the eye for a drop. Also, if the tip of the nozzle becomes contaminated, there is typically no means provided for preventing the contaminated tip from contaminating the medicament within the vial, and thus possibly causing infection by use of the contaminated medicament. Because the medicament in such devices is typically exposed to air upon opening the nozzle, it is not desirable to use such devices to administer preservative-free formulations of medicament, other than by providing single-dose containers. The single-dose containers, however, are typically relatively expensive to package, particularly when used for prescription medications.
The foregoing problems are addressed for a single medicament by the apparatus for applying medicament to an eye which is the subject of my copending application Ser. No. 07/801,243 filed on Dec. 2, 1991. This apparatus comprises a medicament chamber for holding medicament, and a nozzle coupled in fluid communication with the medicament chamber. The nozzle defines a seam which is normally in a closed position for preventing the passage of medicament through the nozzle and which opens in response to the flow of medicament of sufficient pressure to permit the passage of the medicament through the nozzle for release into the eye.
A major advantage of this apparatus is that once a dose of medicament is released, the seam of the nozzle closes, and thus substantially prevents medicament which may have been exposed to air or foreign particles from passing back through the nozzle and into the apparatus, which can contaminate the remainder of medicament in the apparatus. However, the apparatus is not particularly suitable for simultaneously delivering two different medicaments.
Heretofore, in order to deliver two different products (e.g., an antibiotic and an anti-inflammatory drug) simultaneously, or two different drugs used concomitantly for glaucoma (e.g., a betablocker and pilocarpine), it has been necessary to formulate a mixture of the two medicaments. However, there are several problems associated with formulating mixtures. For example, the two drugs often have a different pH and different solubilities which make stable homogenous mixtures difficult or impossible to achieve. In addition, despite the fact that the two drugs may each have FDA approval, a combination of the two is considered to be a new drug which requires, as for a new drug, new pre-clinical and clinical studies, and a separate FDA approval. Moreover, it is often more difficult to obtain approval for the combination because the FDA requires a demonstration of a synergistic effect (i.e., that the combination is more effective than the added individual effectiveness of the drugs administered separately). The development and approval process together can take 7 to 10 years, even for the combination of two drugs already approved separately.
Other packages have been conceived to keep separate two products while on the shelf, and the mixture is to be reconstituted extemporaneously by the patient. But these "double reservoirs" still require a combined formulation for the duration of the treatment, and therefore they must satisfy the FDA regulations for combined products as mentioned previously. In addition, this type of reconstitution package can be very expansive to manufacture.
Yet another problem with the delivery of two different medicaments to an eye is that two ordinary sized drops results in an even greater excess of liquid in the conjunctival cul de sac than the excess which already results with a single drop. Consequently, even more medicament spills out of the eye as waste. For this reason, practitioners usually request their patients to add the two different drops 5 minutes apart. These instructions are frequently not followed by patients, resulting in complications due to the absence of one of the drugs. For example, in the case of Glaucoma, a first drop of medicament does not balance the intra-ocular pressure; only a combination with another drop of medicament will reduce the pressure to a normal level.